Method and apparatus foe indicating



Nov. 9, 1943. w. H. BENNETT METHOD AND APPARATUS FOR INDICATING STORMAREAS Filed July 11, 1941 2 Sheets-Sheet 1 Flea.

I .INVENTOR. WILLARD H.BENNETT ATTORNEY Nov. 9, 1943. w. H. BENNETT2,333,975

METHOD AND APPARATUS FOR INDICATING STORM AREAS Filed July 11, 1941 2Sheets-Sheet 2 38V FIG.4.

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' "1?! M ll/6h VOLTAGE M V M 39 RECTIFIER 35 as 38 k 38 r 36 PIC-3.6.FIG.7.

A.c.sou ec INVE-NTOR. WILLARD H. BENNETT h'lGHl/OLTAGE RECTIFIER. BY MATTORNEY field corona.

Patented Nov. 9, 1943 UNITED STATES) PATENT OFFIQE METHOD AND APPARATUSFOR INDICATIN G STORM AREAS Willard 11. Bennett, Newark, Ohio, assignor,by mesne'asslgnments, to Games Slayier, Newark.

Ohio

.- Application July 11, 1941, Serial No. 402,039

14 Claims. (01. 177-311 an installation on aircraft which will detectthepresence of electrical storm conditions in the vicinity of flight andwill indicate the location of the storm area with respect to theaircraft in ample time to enable the necessary manipulation of theaircraft to avoid contact with the 1 storm area. I

It is one of the principal objectsof this invention to improve the"safety factor of so-called instrument flying by minimizing thetendency,

taken in the past, due to the lack of equipment of this character. j

Another object of this invention is to provide equipment which, inaddition to detecting the presence of high electrical cross fields inthe vicinity of flight and indicating the location of such fields,further functions to discharge current, resulting from precipitationcharging, in

a controlled manner so that this discharge of current does not seriouslyinterfere with radio reception. The dissipation of precipitation chargefrom the aircraft in a controlled manner not only avoids radiointerference from this condition but, a1so,cancels the effect-ofprecipitafor existing electrical conditions to interfere tion chargingon the detecting and indicating with radio reception. Generallyspeaking, interference with radiomeception on an aircraft is dueprincipally to true precipitation charging and a phenomenon commonlyknown as cross When aircraft is flown into an area o'fcharged particles,an electrical charge is deposited on the aircraft, and this conditionmay be defined as precipitation charging. The current, resulting fromthe electrical charge on the aircraft, is discharged from the latter andif this discharge is not controlled, it may reach such proportions as tocause interference with radio reception aboard the aircraft. The WillardH. Bennett et'al. co-

pending application, Serial No. 402,040, filed July 11, 1941, isdirected to a method and apparatus for controlling this type ofdischarge so that it does not seriously interfere with radio reception.

Cross field corona: is very different from pre- 5 cipitation chargingand is'usually much more serious. When aircraft is flying near a chargedcloud, there is an electrical field applied to the aircraft which is thesource of currentboth to trlcal charge on the aircraft may be zero.These currents may be very large and-are a source of 7 radiointerference. i f Q With the above in view, the presentinvention furthercontemplates equipment readily applicable to aircraft for detecting andindicating the location of intense cross electrical field zones longbefore the charged area is able to cause sufficient cross field coronaonthe aircraft to so seriously interfere with radio reception. In otherwords, equipment constructed in accordance with this inventionwillenable the pilot or the aircraft to navigatearound highly charged area'smeans.

In accordance with this invention, the above objects are realized by thestrategic location of points or sharp pointed rods on the aircraft. 'Ithas beenioundthat points require fields above a certain minimum value inorder to become effective and this characteristic of points is commonlyreferred to as the onset threshold field. intensity of the points. Thiscondition is not especially objectionable in discharging precipitationcharge from the aircraft because the onset threshold of the points isdefinitely lower than the portions of the aircraft from which current isliable to discharge directly. However, when using the points to detectand locate electrical cross fields, more sensitive operation ispreferred.

.It is, therefore, a further object of this invention to charge theaircraft with just enough current to overcome the onset thresholds ofthe points. As a result, the points will operate immediately to'indicate the presence of an electric field and, if desired, theintensity of the field may be measured by merely connecting a meter ineircuit with'each point. and from the aircraft, aghough the; net elm--40coeds, especially when considered in connection with the-accompanyingdrawings, wherein.

- Figure 1 is a side elevational view of an aircraft equipped withelectrical discharge apparatus constructed and arranged in accordancewith this invention; .1

Figure 2 is a front elevational'vlew ofthe constrnctionshown in Figure1;

Figure 3 is a sectional view showing one method that may be employed tosecure thepolnted rods to the aircraft;

' Figure 4 is a fragmentary sideelevat ionai view of the tail portion ofthe aircraft:

and thereby avoid dangerous risks that had to be 56 Figure 5 is a wiringdiagram showing the indian area of charged points rather than from thedischarge from the pointed accordingly controlled so that a givenelectrical cating circuit employed in connection with the pointed rods;

Figure 6 is a sectional view ratus employed for placing an electricalcharge on the aircraft;

Figure 7 is an end elevational view'of the construction shown in Figure6;

In Figures 1 and 2 of the drawings, I have illustrated a conventionalairplane l comprising a fuselage H, a tail portion l2, a nose portionl3, and a pair of wings l5, respectively, extending laterally outwardlyfrom opposite sides of the fuselage. In accordance with orthodox design,a motor is mounted on each wing and a propeller I6 is driven by eachmotor.

It is well established that modern aircraft reshowing the appa- Imounted on each of the following. portions of the lies to a great extentupon clear radio reception for safe and accurate navigation. It is alsocommon knowledge that static materially interferes with radio receptionand that under certain conditions of flight, the radio interferencebecomes so critical that the radio is rendered useless. It has beenstated above that this so-called static is due to two somewhat differentconditions which will be-referred to herein as: 1) True precipitationcharging; and (2) cross field corona. It has also been pointed out abovethat precipitation charging is caused by an aircraft flying intoparticles which deposit an electrical charge on the aircraft. Thecurrent. resulting from the electrical charge on the aircraft, isdischarged from the latter and if thedischarge of this current is notcontrolled, it may reach such proportions as to cause interference withradio reception aboard the aircraft. The so-called cross field corona isvery different from precipitation static and is much more critical. Thisphenomenon is usually encountered when aircraft is flown in a regioncontaining one or more electrically charged clouds and may be consideredto be due to an electrical field applied to the aircraft. Thiselectrical field is a source of currents both to and from the aircraft.The

' value of the electrical currents flowing to and from the aircraftincreases as the aircraft proaches the charged clouds and usuallyexceeds thevalue known to cause serious interference with radioreception.

Although the present invention concerns itself more particularly withthe problem of avoiding radio interference from cross field corona,nevertheless, the equipment for accomplishing this result is alsooperative to eliminate the effects of precipitation charging onradioreception. This phase of the problem is described in detail in theBennett et a1. copending application, SeriaLNo; 402,040, filed July 11,1941. However, in order to assist understanding the present invention,reference will be briefly made to the operation of the equipment forremoving precipitation charge.

In general, precipitation charge is removed from the aircraft bystrategically locating a, plurality of pointed rods at differentportions of the aircraft in such a manner that the electrical charge onthe aircraft will discharge from the adjacent portions of the aircraft.As will be presently described, the ends of the rods is the value knownto cause interference with radio reception.

additional points or sharp pointed rods similar to the one illustratedmay be placed at other portions of the aircraft which are liable torelease charge and, therefore, the number as well as the location of thesharp pointed rods -will depend to some extent on the particular designof the aircraft to be equipped.

In the present illustrated embodiment of the invention, the pointedrodsll'and l8 respectively extend outwardly beyond the nose and tailportions of the aircraft, while the pointed rods 19 extend outwardlybeyond the'wing tips of the aircraft. The pointed rods 20 and 2| ,extendvertically for a substantial distance above and belowthe fuselage. Thelength of the rods 20 and 2| is such that the pointed ends projectbeyond the tips of the propeller blades when the latter assume theirvertical positions. The arrangement is such that the points 20 and Mwill project to a greater extent than the propeller blades into 'theelectrical field above and below the aircraft and will operate todischarge electricity which would ordinarily be discharged from thepropeller tip's.

Regardless of the particular locations of the pointed rods on theaircraft, the installation must be such that a given electricalcharge'on the aircraft is discharged from the points in such control theamount of current discharged from any one of the pointed rods and thismaybe accomplished by varying: (1) The length of the sharp pointed rodswith respect to the adjacent portions of the aircraft; (2) The includedangle .ofth'e pointed ends of the rods .or, in other words, thesharpness of thepoints; and (3) The degree of hoodingof the points.

With respect to the length of .the pointed. rods,attention' is called tothe fact that each, pointedrod must have a minimum length which issufficient to insure electrical dischargefrom the pointed ends of therods rather than from the adjacent portions of the aircraft. 'However,

due to the fact that certain portions of the air.-

craft will draw more current than otherportions, it is necessary toincrease the length of certain of the pointed rods with respect to theother rods so that the discharge current will be equally divided betweenthe number of rods.

In the event that the current drawn by any one portion of the aircraftexceeds the amount capable of .being discharged from the adjacent Ipointed rod without causing radio interference, additional pointed .rodsmay be provided at this location in such a manner that the current willbe divided equally between these rods.

In some installations, it may be necessary to extend a pointed rod asubstantial distance from the adjacent portion of the aircraft inorder'to avoid electrical discharge from the latter portion 25 issupported in the wing tip with a reduced portion 26 whic extends later-,1 The target electrode 38 is of the aircraft and at the same time tolimit the current discharged from this point. An instance of thischaracter is shown in connection with the pointed rod 2|! which extendsfrom the top of the fuselage Ii. This condition is compensated for byhooding the pointed end of the rod with a member 23.

may be varied without decreasing the extent to which the rod projectsinto the surrounding electrical field.

The degree of sharpness or the included angle of the pointed rods isalso important in obtaining a radio silent condition.

discharge from sharp points is more steady and the point 36 is betweenone hundred and two Thus, by properly hooding a pointed rod, the currentdischarged from a point @hundred microamperes, the field intensitythrough substantially one half of the radial gap is less than 5 k. v.per centimeter. At 5 k. v. per centimeter the velocity of ions may becon- I sidered to lie-approximately two hundred miles In practically allcases, the pointed ends of the rods should be needle sharp because ithas been found that the less disruptive. For this reason, it isimportant to carefully select the material from'which the pointed rodsare formed so that the rods will withstand the weather without excessiveoxidation, particularly at the points of the rods. Satisfactory resultshave been obtained by forming the rods of steel and by plating thepointed ends of the points with chromium-or rhodium or some othermaterial characterized in that it will protect the ends from excessiveoxidation.

In Figure 3 of the drawings I have illustrated a typicalmounting for oneof the pointed rods.

' More particularly, the mounting for the rod l9 on the wing tip I5 isshown? In detail, a clamp nd is provided ally through an opening in theedge of the wing tip. The reduced portion 26. projects into a recessformed in a block .21 of insulating material and the latter engages theouter skin of the wing opposite the clamp 25. A stud 28 has a reducedshank 29 which extends through the block 21 and clamp 25. The inner endof the shank 29 is threaded for receiving a clamping nut- 30 and thehead of the stud has a threaded bore for receiving the inner end of thepointed rod I 9. This general type of mounting may be used for all ofthe pointed rods and the block of insulating material 21. may beemployed as a hood for the point if desired. In the case tion l2 of theaircraft in the mannerclearly shown in Figure 4. The charger 35comprises a discharge point 38 having the inner end secured in aconical-shaped-holder 31 of insulating ma terial. The holder 31 issuitably secured to the tail portion l2 of the aircraft and supports atarget electrode 38 in the form of a ring which surrounds the tip of thedischarge electrode 36 in the manner shown in Figure 6. The forward endof the discharge point 36 is electrically connected to the output of asuitable rectifier 39 supported in the cabin of the aircraft and capableof energizing the points with a high voltage direct-current. The targetelectrode 38 is grounded on the aircraft and, as 'aaresult, a steadydirect current discharge "of ions takes .place from the. point 38 towardthe target electrode I8.

located in the air of the pointed rod 20, the block of insulatedpreviously described.

per hour, and for an airplane velocity of the same magnitude, the ionswill be blown to the rear and, due the rapidly diminishing fieldintensities, are blowncompletely away'from the airplane.

'I'he particular polarity of the charge left on the airplane will, of.course, depend upon the polarity of the direct. current applied to thepoint 38 by the rectifier 39. In the present instance, I prefer tovenergize the point 36 with a negative potential so that negative ionsare blown off of the airplane and a positive charg is left on theairplane. Assuming that a precipitation charge of positive potential isapplied to the aircraft, it will be' noted that this charge; merely addsto the charge placed on the aircraft by the charger and is removed-bythe pointed-rods. On the other hand, if the precipitation chargedeposited onthe aircraft has a negative polarity, this .-charger and,consequently, does not interfere with the normal operation of thepointed rods It follows rrbm the above that the charger 35 maybe-operated to put a given charge on the aircraft and thereby permitsinitially adjustxing the length; hooding, number and locations of thepointedrods so that the same value of current may be discharged from thepoint on each rod and so that this value of current will be be} low thevalue known to cause radio interference. This adjustment is effectedunder fairweather conditions of flight and when properly made, theequipment will operate satisfactorily to remove precipitation chargefrom the aircraft .witliout causing interference to'radio reception. Itwill,

of course, be understood that when making the i above adjustments. 9.meter M is-electrically connected to eachpointed rod in th mannerindicated-dn Figure 5 so that the current discharged by eachro'd may bereadily ascertained.

Referring now to the cross field corona conditlon briefly'describedabove, it will be noted as this description proceeds that the presentinvention contemplates minimizing the danger result- 1 ing from thiscondition by warning the pilot-of the existence'of an intense electricalfield and by indicating the location ofthisfleld with respect to -theaircraft so as to enable the pilot to navigate around thestorm or highlycharged area.

In general, the existence of an electrical field or,

charged clo'udis conveyed to the pilot by'means of electrically operatedsignals connected in circuit with thepoints and operated by the currentspassing to and from the aircraft. Hence, the

sensitivity of the pointed rods is importantin I Figure 5 of thedrawings indicating electrical fields, andin order to im.-

prove the sensitivity of the pointed rods, the by the char er 35 withjust latter are energized enoughcurrent to overcome the onset thresholdsdrfleld intensities of the pointed rods.

-With the above in view,

wherein it will be noted that the pointed rods l'I and I! areelectrically connected to ground through the medium of reattention 15called to sistances 4n and 4| respectively. An electrically operatedsignal in the form of a gas filled tube 42 is connected across thepointed rods 11, I8 and a condenser 43 is also electrically connectedacross the pointed rods so as to discharge through the tube 42. Thefuselage points and 2| as well as the points on the wing tips arerespectively electrically connected to ground in the same manner as thepoints l1 and 18.

Although the voltage of the output rectifier 39, value of theresistances and M, capacity of the condenser 43 and type of the gasfilled tubes 42, 44 and may all vary in accordance with differentconditions, nevertheless, a satisfactory operating condition has beenobtained by employing the following specifications. The voltage of theoutput rectifier 39 depends largely on how fast and how high it isdesired to charge the aircraft with the charger 35. Satisfactoryoperation has been obtained with output voltages in the range of ten totwenty thousand volts. The value of the resistances 40 and 4| and thecapacity of the condensers 43 depends on the desired sensitivity of thewarning signal circuits. The resistances are not particularly criticaland may be varied between one to five hundred megohm in cases where thecondenser capacity is .01 Mfd. In connection with the types of gasfilled tubes employed, it has been found that "RCA #991 neon" tubesoperate satisfactorily.

It follows from the foregoing that currents passing to the nose and tailpoints I! and 18,

respectively, flow through the resistors 40 and 4! respectively. As longas the-current consists only of a uniform charging current supplied onlyby the charger 35 plus a greater or lessamount of precipitationcharging, or, in other words, when each point is discharging the samamount of current as the other points, the voltage across the signaltube 42 is zero. However,"a soon as there is any electrical fieldapplied to the nose or tail of the aircraft, the current from one of thedischarge points is suppressed by the field, resulting in a voltageapplied to the signal tube 42. This, condition causes the'condenser 43to discharge through the signal tube 42in a manner to repeatedly give awarning series of flashes in the tube which become a continuousillumination for strong fields. Thus, if the aircraft is approaching anelectrical field, the point I1 draws a curientand energizes thesignaling tube 42. As the aircraft approaches the electrical field, thevalue of the current drawn by the point I! increases and the periodicityof the flashes. in the signaling tube'42 correspondingly increaseuntil'the current becomes suflicient to continuously illuminate thesignaling tube 42. Thi gives suificient warning to the pilot that theaircraft is approaching a complicated storm area and'enables the pilotto navigate around the stormarea or to land the aircraft-at the nearestairport. In the event that the charged cloud or electrical 'field isabove or below'the aircraft, either the point 20 or the point. 2|energizes the signaling tube 44 in the same manner as described above.On the other hand, if the highly charged cloud or electrical field is oneither side of-the aircraft, one of the wing tip points energizes thesignaling tube 45' toindicate the location ofthis charged area. Thus,

-' regardless of the location of the storm area, pro- -vision is madefor detecting the same and the sensitivity of the points is such-that awarning is" given tothe pilot in ample tim for him to navi gate aroundthe storm area or to land the airdifference of potential between theaircraft and atmosphere, means for respectively electrically groundingthe rods on the part aforesaid of the aircraft through resistances, acondenser connected across the rods, and a signaling device electricallyconnected across the condenser.

2. Aircraft havin a point projecting therefrom and adapted to beenergized by an electric field in the region of flight of th aircraft,means for supplying sufi'icient current to the point to overcome theOnset threshold thereof and thereby increase the sensitivity of thepoint to electric fields, and means for indicating energization of thepoint by an electric field in the general vicinity of the aircraft.

3. Aircraft having a part adapted to conduct electricity, pointsprojecting outwardly from different portions of said part of theaircraft and adapted to be energized by a difference inpotential betweenthe aircraft and the surrounding medium, said points having anelectrical resistance connection with the part aforesaid of the aircraftand being adjusted to discharge equal amounts of current, means forputting an electric charge on the electrically conducting part of theaircraft to supply su'fiicient current to the points to overcome theonset threshold of the points, an electrically operated signal connectedacross the points, and a condenser connected across the signal.

4. In an airplane having nose, tail and wing portions, points projectingoutwardly from the nose and tail portions, a second set of pointsproiecting outwardly from the top and bottom por-' tions of theaircraft, a third set of points provalue of current, means for supplyingsufficient ,tain substantially current to the thresholds of the signalassociated means respectively nals to the sets of points to overcome theonset points, an electrically operated with each set of points, andelectrically connecting the sigpoints and operable to mainzero voltageacross the signals as long as said points discharge equal amounts ofcurrent.

5. In aircraft adapted to carry a charge of an electric conductingelement proelectricity,

jecting from and grounded on the aircraft, means electricity,

for placing an electric charge on the aircraft to supply the current-tothe conductor element required to overcome the onset thresholdcharacteristic thereof and thereby increase the sensitivlty of theelement to electric fields in the vic1nity of the aircraft, and meansfor indicating energization of thesaid element by an electric field thegeneral vicinity of the aircraft.

6. In aircraft adapted to carry a charge of which charges of electricityare most likely to escape when adiil'erence of potential exists be-'tween the aircraft and atmosphere and adapted to be energized by anelectric field in the general vicinity of the aircraft, and

means for indicating by an electric field in the vicinity of theaircraft.

a pluralityof electric discharge members grounded on those parts of'theaircraft from.

7.111 aircraft of the type adapted to carry 'Jan' electric charge, aplurality of pointed rods extending outwardly from the portions of thetential drop so determined with'respect tothe potential dro'p,of theother rods thatsubstantially the same amount .of current is dischargedby eachrrod when a potential difierence exists between the aircraft andsurrounding medium, said rods also being sensitive to electric fields inaircraft from which electric charges are most likely to escape, eachpointed rod having a pothe general vicinity of the aircraft and adaptedA to be energized thereby, and means for indicat Y ing 'energ'ization orone or more, of the pointed rods by an electric field in the generalvicinity of the aircraft.

8. In aircraft of the type adapted to carry anelectric charge, aplurality of pointed rods extending outwardly from the portions of theaircraft from which electric charges are most likely to escape, eachpointed rod having a potential drop of the other rods that substantiallythe same amount of current is discharged ;by each red when apotentialdifierence exists between the aircraft;. and surroundingmedium. -m eans for u ply ng sufilcient current to eachrod to overcometheonset threshold characteristics thereof and thereby increase thesensitivity of the rods to electrical fields in thegeneral vicinity ofthe aircraft, and means for indicating energization potential existsbetween the aircraft and surrounding atmosphere, means for supplyingsuflicient current to the conductor elements to overcome the onsetthreshold characteristics of said elements and-thereby increase thesensitivity of the elements to electric fields in the general vicinity'of the aircraft, an'electrically operated signal for each set ofconductor elements, and means respectively electrically connecting thesignals to the sets of conductor elements to indicate energiz'ationthereof by electric fields and operable to maintain substantially zerovoltage across the signals when the conductor elements are passingsubstantially equal amounts of current.

12. In aircraft of the type adapted to carry an electric charge, aplurality of electric discharge elements grounded on and projectingoutwardly from the aircraft in different directions, each disdrop .sodeterminedwith respect to the potential of. the pointed rods by anelectric field and for also indicating the general direction or thefield from the aircraft.

'9. Aircraft having points proiectingoutwardly.

therefrom and adapted to'be energized by an electric field in the regionof flight o! the air- 'craft, each point having a potential dropdetermined with'respect to the potential drop of .the other points thatsubstantially the same amount of current is discharged by each pointwhen a diiference of potential exists between the.

aircraft and surrounding medium, means for supplying suflicient currentto the points to substantially, overcome the onset threshhold charac-.

teristics of the points, an electrically operated.

signal, and means electrically connecting the s18-- nal to. the pointsand operable to maintain substantiallyjz'ero. voltage across the signalwhen the points are passingeqlw amoimts of current gizaticn of one ormore of the po nt! y n electric field in the general vicinity of theaircraft...

'to be energized thereby, and means for indicating energizationof theelements by an electric V field and for also indicating the generaldirection of the field from the aircraft including signals respectivelyelectr ally connected to the disc rge elements v 13. Aircraft having aplurality of sets of elec tric conductor elements projecting therefromin different directions and each element having a potentlal'iirop sodetermined with respect to the potential drop of the other elements thatsubstantially the same amount or current is dis- .chargedby each elementwhen a difference of potential exists between theaircraft andsurrounding atmosphere, said elements also being sensitive to electricfields in the general vicini y oi.the aircraft and'adapted to 'beenergized by the fields, an electrically operated for each set ofelements, and means-respectively electrical- 1y connecting the signal tothe sets of elements andtoeifect operation oftheaishalu'pon ener- 10.aircraft having aplurality of electric'con- 'ductor elements projectingtherefrom insurer-eat directions and adapted-to be energized by anelectric field in the-region of flight of the aircraft,

.'means for supplying current to the conductor elements. to overcome theonset threshold charac-' teristics thereof and thereby increase thesensitivity or the conductor elements to electric fields in the generalvicinity of the'aircraft, and means for indicating the element'orelements.

'by the electric field to thereby indicate the direc tion of theelectric'field from the aircraft.

llrAircraft having a pluralityofsets of -e1eetric conductor.elementsprojecting therefrom in different directions and each elementhaving a potentialdrop so determined withrespect to the potentialdrop'of the other elements that sub- .-stantially. the same amoimt ofcurrent is diacharged-by each element when a diiierence of r to imiieatenergization thereof by electricfields gand operable to maintainsubstantially zero Voltage across the signals when the conductor; mentsare I substantially. equal amounts of current. 1'

l4. :Aircrait having points projectingoutwardly'fromtheportionsoftheaircraftfromwhich electric charges aremostlikely to escape and ,adaptedtobeenergizedbyelectricfieldsin'the'general vicinity of the aircraft, each point hav- 'ingapotentialdropaodetermined with respect to the potential drop of the otherpoints-thatamoimtofcurrentisdischargedbyeachpointwhenadifferenceofpotentialexistsbetweentheaircraftandeum. an w We Q means electrically connecting'the signal am-L d p intsandoperabletomaintain J 1... aerovoltageacrossthesignalwhenthepointsareequal amountsofcurrent and'tothereby eflect operation of the signal W n81 m ofoneormoreofthcpointsbyanelectricfield in the region of theaircraft.

